Process of producing motor fuel



March 17, 1936.

W. M. STRATFORD PROCESS OF PRODUCING MOTOR FUEL Filed June 20;

W/L/HM M 575/477080 INVENTOR BY W QNI

Patented Mar. 17 1936 UNITED STATES PROCESS F PRODUCING MOTOR FUELIWiuiarrr M. Stratford, New York, N. Y., assignor to The Texas Company,New York, N. Y., a corporation of Delaware Application June 20, 1932,Serial No. 618,123

4 Claims.

'Ihis invention relates to the treatment of hydrocarbon oils and moreparticularly to the treatment of distillates obtained by crackingpetroleum or other hydrocarbons which may contain un- 5 stable,unsaturated compounds.

'Ihe invention contemplates a method of treating and purifyinghydrocarbon oils such as cracked naphtha, which contain undesirable,unsaturated compounds, which includes contacting the naphtha undersubstantially liquid phase conditions and at elevated temperature undersuperatmospheric pressure, with a suitable contact catalyst whereby saidundesirable, unsaturated compounds are polymerized to compounds ofhigher boiling point, distilling the treated naphtha from, said higherboiling polymerized compounds, and then contacting the treated distillednaphtha under vapor phase conditions with a suitable contact catalystwhereby any remaining undesirable, unsaturated compounds are'polymerized to compounds of. higher boiling point thanthe treated andpurified naphtha and are thereby separated from said naphtha.

When hydrocarbons such as crackednaphtha and the like, containingcertain types of unstable and undesirable, unsaturated compounds, forexample, the diolefines, are contacted at elevated temperatures and inthe yliquid state with catalytic adsorbents whichare active at suchtemperatures, a polymerization of the unstable, unsaturated compounds'takes'place. Such a polymerizationresults in the formation of new'compounds known as polymers having boiling points higher than those ofthe original unsaturated compounds. This characteristic of the polymerspermits oi.' their ready separation from the treated naphtha by means ofa distillation of the liquid treated product in which they arepresent.

Such liquid phase methods of treating cracked Lto naphtha may besatisfactory for the treatment of most types of naphtha distillates.

thecase -of some of the more highly unsaturated distillates produced bycertain speciiic cracking conditions, the products of a liquid'treatment may 4.5 be unstable when exposed to oxidation or to longstorage. This instability may' be due either to the presence of smallquantities-of undesirable,

' unsaturated compounds remaining in the oil or to partly polymerizedcompounds which have been 5o formed during'the liquid phase treatment.This characteristic may not be due to any inherent deficiency of theliquid phase treating process but may result from the factl that asufiiciently long time of contact between the oil and the 55 catalyticadsorbent is not economically possible.

However, in

It is appreciated that by subjecting hydrocarbons containing unstable,unsaturated compounds to a treatment in the vapor phase with certaincatalytic adsorbents, that averycomplete separation of these unstablematerials is possible 5` without in any way eiiecting those unsaturatedcompounds which, by their presence, enhance the anti-detonatingqualities of the product. \It is not, however, suited to the treatmentof hydrocarbons containing large percentages of unsaturated bodies sincethese, when polymerized, have a tendency to be adsorbed and may poisonthe catalyst.

In accordance with the invention, the advantages of treating crackednaphtha both in the l5 liquid and in the vapor phase are obtainedyielding results not obtainable by the employment of either methodalone. The liquid phase treatmentl serves as a. vigorous means ofremoving ythe bulk of the unstable, unsaturated compounds. Be- 20 causeof the higher pressures and higher temperatures employed in thistreatment the actual polymerization per unit weight of catalyst employedis high and the polymers which are formed are continuously andconcurrently washed out 25 of the adsorbent by the associatedportions ofthe naphtha.` The vapor phase treatment which is carried out at asomewhat lower pressure and temperature serves effectively' topolymerize and separate any undesirable, unsaturated' constitu- 30 entswhich may not have been removed or which may have been formed during theliquid phase treatment. y v

Thus, by the practice of the present invention, cracked napthas derivedfrom any type of crack- 35 ing process and including those naphthaswhich lare particularly refractory to ordinary treating methods, can bepurified and stabilized to yield motor fuel of a most satisfactorymerchantable quality.

A particular advantage of the invention lies lin the fact that each ofthe two processes oi.' treat- K ing may be worked at their highesteiliciency withoutl decreasing substantially the lives oi' theadsorbents.

'Ihe inve'ntion willk be fully understood from the following descriptiontaken inconnection with the drawing whichrepresents in diagrammaticsectional elevation, an apparatus whichy may\be employed for carryingout the process. 504

The apparatus illustrated in the drawing is' shown and described merelyfor the purpose oi" aiding `and understanding the process and it is toybe understood that any other suitable apparatus may be substituted forthat shown. v

42 controlled by the automatic Vvalve 43.

In the figure, the numeral I designates a storage for a supply of acracked naphtha distillate which is to undergo treatment. 'Ihis storageis connected through the line Il controlled by valve I2 with the inletof the charge pump I3. 'I'his pump is connected through the line I4 withthe coils I5 of a suitable heater I 6, which may be of any of theconventional types.

The outlet of the heater coils is connected to the line I1 controlled bythe Valve I8, which line enters .the high pressure treating chamber I9at a lower point in its structure. The bottom of this pressure treatingvessel.is provided with a draw-oir line 20 controlled by the valve 2|.Situated within this treating vessel there is a bed of a suitablecatalytic adsorbent, such for example as fullers earth, the character ofwhich is dependent upon the operation of the process. The top of thetreating chamber I9 is provided with a liquid draw-oir line 22 which isfitted with a high pressure gauge 23 for following the pressuresexistent within the pressure treating vessel. The draw-oir line 22connects with an expansion valve 24, the outlet of which is in turnconnected by a line 25 to a lower point of the fractionating tower 21.'Ihis line 25 is provided with a pressure gauge 26 which assists incontrolling the extent of the expansion possible by the manipulation ofthe expansion valve 24.

The fractionating tower 21 may be of the conventional type, soconstructed as to withstand the pressures to which it may be subjected.It is fitted at its lowest point with a draw-off line 28 controlled bythe valve 29. Into a lower point of its structure there is tted a steamspray 30 which is provided with a control valve 3|.. At an upper pointof the fractionating tower there is situated the cooling coil 33, thepurpose of which ,is to supply reflux cooling for fractionation. Atpoints intermediate the top and bottom of the tower there are introducedlines 34 and 35 controlled respectively by the valves 36 and 31 whichserve a function which will be hereinafter described.

The uppermost point of the fractionting tower 21 communicates throughthe vapor line 38, controlled by the valve 39 with the top of thesuitably insulated Vapor treating tower 40. Situated within this towerthere is a bed of suitable adsorbent catalyst such as fullers earth orthe like. This bed of catalytic adsorbent may be advantageouslysupported upon a reinforced screen 4 I; however, any other satisfactorymethods of supporting the bed of` adsorbent catalyst may be used. Thelowest point of the vapor treating tower40 is fitted with@ draw-off lineThe discharge side of this Valve is provided with the line 44 controlledby the valve 45 which line may lead to a suitable storage chamber.

There is tted into the line 44 a'branch line 49 controlled bythe valve46 which communicates with the inlet side of the recirculating pump 41which pump in turn discharges into the line 48. Thisline connects withboth the lines 34 and 35 which enter the fractionating tower 21 atvarious points as shown.

Below the bed of catalytic adsorbent a vapor draw-off line 50, which maybe protected from any descending liquid by the baille plate 5I, isconnected through the valve 52 with a lower pointv of the fractionatingtower 54. The bottom of this fractionating tower 54 is fitted with aline 55 controlled by the valve 56. Leading into this line there is theline 51 controlled by the valve 58 which enters the line 49 at a pointintermediate the valve 46 and the pump 41. At a lower point in thefractionating tower structure there is provided a steam spray 66controlled by the valve 6I. At an upper point in the fractionating towerthere is situated a cooling coil 62 which is'used for supplying refluxcooling.

The uppermost point of the tower 54 is provided with a vapor draw-oirline 63 controlled by the valve 64 which communicates with the inlet ofthe condenser coil 65 of the condenser 66. The outlet of the condensercoil enters the line 61 controlled by the valve 68 which linecommunicates with the separator 10. The bottom of this separator isfitted with a liquid draw-off line 1I controlled by the Valve 12 whichline communicates with a suitable storage tank (not shown) for theliquid product. The top of the separator chamber is supplied with avapor drawoif line 13 controlled by the valve 14 which line connects theVapor space of the separator with a gas compression plant or a suitablestorage for the gases produced in the process.

In the operation of the process in connection with an apparatus such asthat illustrated in the figure, a cracked naphtha distillate, which mayv contain a varying percentage of hydrocarbons suitable for use as motorfuels, is drawn from the naphtha storage tank I0 and delivered to thecharge pump I3. 'I'his pump is of the high pressure type capable ofdelivering oil under pressures of from 1000 to 3000 lbs. per sq. in. ormore. The naphtha is pumped through the heating coils I5 of the heaterI6 where itsrtemperature may be raised to a suitable working temperaturewhich may be in the range of from 400 to '700 F. Under the existingpressures which may be the full working pressure of the charge pump I3the naphtha is maintained substantially in the liquid phase.

It may be desirable to submit the untreated naphtha to a preliminarystabilizing operation whereby low boiling` hydrocarbons andnon-condensable gases may be substantially removed. Such compounds ifallowed. to remain in the naphtha would be selectively adsorbed by theadsorbent and in this m'anner would reduce the over-all eiiiciency ofthe catalyst and of the polymerization.

The heated naphtha is delivered from the heater coil outlet through thevalve I8 and passes into the high pressure treating chamber I 9 where itis forced through the bed of catalytic adsorbent which is presenttherein. The treating chamber is heavily insulated and a temperature of400 to 700 F. is maintained therein, the pressure. being preferably inexcess of 1000 lbs. per square inch. By controlling the rate of chargeof the heated oil through the pressure vessel, the time of contactbetween the oil and catalytic adsorbent may be closely controlled.During this period of contact, the lcatalytic adsorbent brings about thepolymerization of the unstable unsaturates present in the untreatednaphtha distillate. Some of the polymers which are formed in this 'waymay become absorbed by the 'adsorbent but,'under the conditions oftemperature and pressure existing in the treating chamber, the greaterportionof the polymers are dissolved by the naphtha with which they forma solution.

This solution of polymers in naphtha is drawn off from the pressuretreating vessel through the line 22 and the expansion valve 24 where theliquid is ashed into a vapor. The extent of this vaporization iscontrolled by the diierence in pressure existing between the highpressure liquid phase chamber I9 and the pressure maintained in thefractionating tower 21 into which the vapors are flashed. The magnitudeof the desired in final treated motor fuel. In the course of thisfractionation all those higher. boiling polymers which were formed inthe liquid phase treatment are substantially separated and are drawn oifas a residue from the bottom of the tower through the draw-olf line 28.The desired vapor fraction having, for example, an end-point of about410 F., is drawn oif from the top of the tower through the vapor line 38controlled by the valve'39 and introduced into the top of the vaporphase treating tower 40. l'I'he vapors are then caused to pass throughthe bed of adsorbent catalyst in the tower 40, whereby any remainingunstable, unsaturated compounds are transformed into higher boilingpolymers. These polymers separate as liquids since the temperaturesmaintained in this treating chamber are below the temperatures ofvaporization of the polymers.l They collect as a liquid together with acertain quantity of unvaporzed naphtha at the bottom of the tower .fromwhich they are drawn off through the line 42 controlled by the floatcontrol valve 43. They may be either passed to a suitable storage tankor they may be caused to pass to the recirculating pump 41 whichydelivers them under sufiicient pressure so that they may be introducedinto the fractionating tower 21 at one or more levels in the towerstructure such asthe points 34 and 35.

The treating tower is preferably operated under a pressure of about 400lbs. per square inch and,l although heavily insulated, enough heat isradiated to eifect some condensation of vapors therein.

'I'he vapors are drawnroif through the line 50 and the valve 52 andpassed into the final fractionating tower 54. By the proper manipulationof the valves controlling the various lines entering the vapor phasetreatingchamber, working pressures which may vary from thatvmaintainedin the fractionating tower 21 to a pressureonly slightly aboveatmospheric may be caused to be r maintained therein. In thefractionating tower 54 which has previously been termedl the finalfractionating tower, a vapor fraction having the boiling range desiredin the flnal motor fuel is prepared. Hydrocarbons having boiling pointshigher than the end-point of the nal treated product separateas liquidsand are drawn off from the bottom of the tower through the line 55controlled by valve 56.

In certain operations of the process it may be desirable to recirculatethese residual hydrocarbons to the fractionating tower 21 which isaccomplished by causing them to enter the line 43 through the line 51controlled by valve 58 which connects line 55 with line 49.

In order to bring about complete separation of .the desired vapors fromthe residual oils in the bottom .of the tower 54, it may be desirable tointroduce steam into the bottom of the tower y through the steam spray60. vThe final treated vapor fractionwhich is drawn off fromvthe top.

of the tower is then delivered through the line 63 and the valve 64 intothe condenser coils 65 of the condenser 66 where a substantialcondensation is caused to take place. The condensate isdrawn olf throughthe line 61 controlled by the valve 68 and delivered into the separatorchamber 10 where a separation of undesirable light hydrocarbons andnon-condensable gases is caused to off from the bottom of the separatorchamber through the line 1I controlled by 'the valve 12 and delivered toa suitable storage tank.

The separated undesirable light hydrocarbons and non-condensable gasesare drawn oif from the vapor space of the separator chamber anddelivered through the line 13 controlled by the valve 14 to a gascompression plant or a vapor storage system. In those operations wherethe .vapor phase treatment is carried out under substantial pressures,it may be found desirable to carry out the condensation of the treatedvapors under pressure. This is most advantageously accomplished by theproper manipulation of the Valves 64 and 61 which control respectivelythe inlet and the outlet of the condenser coil 65 of the condenser 66.

In the operation of the herein' disclosed process, it may be desirableto use adsorbent catalysts such as fullerfs earth or the like in boththe liquid and the vapor phase treating steps. It may be preferable,however, to use in either one or both of the steps an adsorbentdecolorzing clay of the montmorillonite type which has been subjected toa treatment with acid and which exhibits its\ greatest efciency attemperatures in excess of 250 F. when used for decolorzing lubricatingoils. A material of the type referred to is disclosed in the U. S.Patent No. 1,642,871

issued to Marvin L. Chappell, Richard F. DavisV and Merle M. Moore.

After the activity of the adsorbent in'either one or both of the stepshas been decreased to such an extent so that it will no longer perform`itsfunction, it may be found advantageous to stop operating and to treatthe adsorbent with saturated or superheated steam. This treatment willtend to remove those polymers which have become adsorbed on the clay andwhich may have in that way reduced its activity to a low value.

Obviously many modiiications and variations take place. The finaltreated motor fuel is drawn of the invention, as hereinbefore set forth,may y' be made without departing from the spirit and scope thereof, andtherefore only such limitations should be imposed as are indicatedin-the appended claims.'

I claim:

1. The process of producing motor fuel having a good color and a low gumcontent band having good storage properties from a highly crackednaphtha distillate containing undesirable, unsaturated hydrocarbonswhichcomprises heating the naphtha distillate to a temperature in the rangeof from 600` to '700 F. while maintained in the liquid phase under apressure in 'excess of 1000 lbs. per square inch, passing the heatednaphtha without substantial reduction in temperature or pressure througha bed of fullers earth whereby a portion of the undesirable, unsaturatedcompounds is polymerized 'to com'- pounds of higher boiling point,substantiallyreducing the pressure vto eect distillation of said naphthaby the contained heat thereof whereby vapors are evolved free from thehigher boiling polymerized compounds, passing said vapors under apressure of approximately 350 to 500 lbs. per square inch through a bedof fullers earth whereby remaining undesirable, unsaturated compoundsare polymerized to compoundsA of higher boiling point, and separatingsaid polymerized compounds Yfrom the treatedand puried naphtha.

2'. `The process of producing motor fuel having a goed color and a lowgum content and having good storage properties from a highly crackednaphtha distillate containing undesirable, unsaturated compounds whichcomprises heating said naphtha distillate to a temperature of above 4501i'. but below that at which substantial cracking yoccurswhilemaintained under a pressure of the order of 1000v pounds per squareinch or more, passing the heated naphtha while maintained at suchpressure through a bed of solid catalytic adsorbent material whereby a`portion of the undesirable, unsaturated compounds is polymerized tocompounds or" higher boiling point, subjecting said naphtha todistillation and recn tincation whereby vapors are evolved free fromsaid higher boiling polymerized compounds, passing said rectied vaporsthrough a bed of suitn able catalytic adsorbent material maintainedunder a pressure not higher than 500 pounds per square inch wherebyremaining undesirable, unsaturated compounds are polymerized tocompounds of higher boiling point, and separating said polymerizedcompounds from the treated and purined naphtha.

3. The process of producing motor fuel having a good color and a lowlgum content and having goed storage properties from a highly crackednaphtha distillate containing undesirable, unsaturated compounds whichcomprises heating said naphtha distillate to a temperature of about 450to 700 F. under a pressure in excess of 1000 lbs. per square inch,passing the heated naphtha without substantial reduction in temperatureor pressure through a bed of iullers earth whereby Aa portion of theundesirable, unsaturated compounds is polymerized to compounds of higherboiling point, substantially reducing the pressure to effectdistillation of said naphtha by the contained beat thereof wherebyvapors are evolved free from said higher boiling polymerized compounds,passing said vapors under a pressure of approximately 350 to 500 lbs.per square inch through a bed of fullers earth, whereby remainingundesirable, unsaturated compounds are poly-= merized to compounds ofhigher boiling point, and separating said polymerized compounds from thetreated and purified naphtha.

4. The process of producing motor fuel having a good color and a low gumcontent and having good storage properties from a highly cracked naphthadistillate containing undesirable unsaturated compounds, which comprisessubjecting the naphtha, while maintained at an elevated temperatureabove 450 F. but below a cracking temperature and under a pressure offrom 1000 to 3000 pounds per square inch, to Contact with a suitablecatalytic adsorbent material to eiect a polymerization of`a portion ofsaid undesirable unsaturated compounds to compounds of higher boilingpoint, subjecting said naphtha to distillation and rectification under alower pressure to eirect a separation of said higher-boiling polymerizedcompounds in liquid form while withdrawing naphtha constituents in vaporform, subsequently subjecting naphtha constituents in vapor form tocontact with catalytic adsorbent material at a temperature and pressurelower than those obtaining in said previously-mentioned high pressuretreating stage to eiect a polymerization of remaining undesirableunsaturated compounds to compounds of higher boiling point, andseparating said polymerized compounds from the treated and puriednaphtha.

